652 
3 
•py 1 



UNIVERSITY OF 

SOUTHERN CALIFORNIA 

PUBLICATIONS 



Volu 



LOS ANGELES, CALIFORNIA 
MARCH 1915 



Number 1 




NITRATING THE SOIL 
BY INOCULATED LEGUMES 



Baileg 



UNIVERSITY OF 

SOUTHERN CALIFORNIA 

PUBLICATIONS 



Volume 2 



LOS ANGELES, CALIFORNIA 
MARCH 1915 



Number 1 




NITRATING THE SOIL 
BY INOCULATED LEGUMES 

BY 

GILBERT ELLIS BAILEY, A.M., PH.D. 

Professor of Geology 






Copyright 1915, by Gilbert Ellis Bailey 
All Rights Reserved 



Printed by the University of Southern California Press 
3474 University Avenue, Los Angeles 
/ 

MAR 30 1915 

(0)CI,A:iiV8 142 



FOREWORD 



Agriculture is no longer simply a method of getting a liv- 
ing, but is a real business enterprise managed and controlled 
with scientific accuracy and all engaged in it are ever hunt- 
ing for new secrets of success. 

This paper has been prepared partially to answer numerous 
inquiries impossible to answer by mail, but mainly to call 
attention again to one of the duties everyone who tills the 
soil owes to the Nation, and in that sense it is an appeal to 
patriotism. 

The intention is to be practical rather than technical, for 
the man engaged in farming wants to know the points of 
practical value in a positive or negative way. No claim of 
originality is, nor can be, made in work of this kind, but 
some of the authorities consulted are referred to by num- 
ber for the benefit of those who wish to study some points 
more fully. 

All know that the soils of Palestine, which once flowed 
with milk and honey, are now a barren waste. Everyone 
realizes that the fertility of soils ought not to be reduced; 
that high civilization cannot be maintained unless there is 
an abundance of food products. Many know that NITRO- 
GEN is the most expensive and difficult plant food there is 
to get, especially at the present time when nitrate of soda 
is contraband of war. Some know that Nature has a remedy 
for the deficiency; that it is possible to obtain unlimited 
supplies of NITROGEN from the air at small cost, by means 
of inoculating legumes with nitrogen bacteria. 

Success with nitrogen bacteria is a simple and not difficult 
combination of science and sense and calls for only moderate 
thoughtfulness and care. 

Inoculation of soils has already passed the experimental 
stage and is established as an agricultural necessity. Farming 
without the aid of bacteria would be an impossibility for the 
soil would yield no crops. 



4 University of Southern California 

The soil is the support of agriculture, and agriculture is 
the support of the nation. It is evident, therefore, that an in- 
telligent control of the beneficial bacteria is a matter of 
National importance. 

The wealth of a State lies in her soil, and her strength lies 
in its intelligent cultivation. The final destiny of America 
in fact rests upon the question whether the producing 
power of the soil shall be reduced, maintained, or increased; 
and this productiveness must not be temporary but perma- 
nent. 

The great sciences of physics, chemistry, geology, and bac- 
teriology are the servants of agriculture standing, as it were, 
with bared arms ready to serve our present and future needs. 
Agriculture is coming to be a scientific pursuit, and farming 
is now recognized as a learned profession. The successful 
farmer of tomorrow will be the one who knows how to han- 
dle most skillfully the micro-organisms in the soil. 

The imperfect methods of the past led to waste, and the 
culminating point of success in the future can only be reached 
under the most capable management. The brain farmer is 
slowly but surely crowding out the muscle farmer; for work 
and knowledge are a stronger team than work and work. 

The rate of progress is still too slow for there is scarcely an 
area in the world that is producing for man the quantity of 
food that it should. In the last ten years our population 
has increased 21 per cent, while the acreage of farm lands 
increased less than 5 per cent; and the average production 
per acre is far below that of European countries. 

Increased population has led to increased demands with- 
out an increased source of supply. The increased value of 
farm lands makes it necessary to get more out of the soil 
than ever before, yet the ten year average of wheat in the 
United States is only 14 bushels per acre. Compare this 
to the 29 bushels of wheat per acre raised in the older soil 
of Germany; the 33 bushels raised in Great Britain; and 
the more than 40 bushels raised in Denmark. (46.) 

Americans waste plant food. We do not return what we 
take from the soil. If we keep drawing from our capital. 



Nitrating the Soils 5 

without making deposits from time to time, our drafts will 
not be perpetually'honored. The merchant sells and buys 
again keeping up his stock; the farmer sells, and sells, and 
sells, until he is practically gold out. The parable of the 
talents is as significant now as when it was uttered; and to 
us are given talents never given before. 

The fate of the Nation lies in the progressive farmers who 
do not bury their talents but keep them alive; the men 
whose public spirit, patience, and watchful care maintain 
the fertility of the soil. , ^' 

KEEP UP THE FERTILITY%TtHE SOIL! Do not 
leave your children with only a mernory or a tradition of the 
bountiful harvests of former times. The owner should in- 
crease the fertility of his land for his children's sake; the 
tenant should leave the farm better than he found it If 
he who "makes two blades of 'grass grow where one grew 
before is a benefactor," then he who reduces the fertility of 
the soil is a public curse. For the sake of humanity, for 
the sake of our own nation see that the land does not grow 
poorer but richer from year to year. 



THE BACTERIA 

All organic matter, that is all dead animal and vegetable 
material, begins to decompose, decay, or rot as soon as it is 
buried in the soil. 

This is Nature's method of sanitation, and of keeping per- 
fect the cycles of life. Everything is at once taken apart 
and each part made ready to use over again. (31.) 

This work is done by various kinds of bacteria, each hav- 
ing its specific task to perform. There are two varieties 
present in all soils, to a greater or less extent, whose work 
it is to separate the nitrogen from the complex organic com- 
pounds which are useless for plant food. One variety con- 
verts the nitrogen into nitrites, and the other converts these 
into soluble nitrates; a form that can be used by plants as 
food. 




U. S. Dept. Agriculture. 



COWPEA TUBERCLES 



Nitrating the Soils 



There is a still more valuable kind of bacteria that possess 
the peculiar and most valuable power of TAKING NITRO- 
GEN FROM THE AIR AND 
NODULE BACTERIA CONVERTING IT INTO NI- 
TRATES, ready for use by the 
plant as food. These bacteria live in nodules on the roots of 
leugmes, and are generally known as the nitrogen bacteria. 
(1, 5.) 




U. S. Dept. Agriculture. 
Roots of Red Clover Showing Nodules 

They are single-celled organisms somewhat closely allied 
to the yeast plant; and are as harmless to man, beast, or 
plant, as the yeast germ itself. 

They are classified as plants but are on the border line 
between the animal and vegetable kingdom where any 
strict division must be a purely arbitrary one. Analysis 
shows that they are about 80 per cent water; tlie ash con- 



8 University of Southern California 

sisting largely of phosphoric acid, with notable quantities of 
potash and lime; while there are only traces of sulphur, iron, 
magnesium, and silica. (8, 6, 14, 36, 37, 38,) 

In method of reproduction they are classed with the 
schizomycetes, or fission fungi, for they multiply by elongat- 
ing a little and then dividing into two equal halves; each half 
soon growing to mature size, ready in turn to divide. They 
are so minute that 25,000 of them would only make a line 
an inch long, and they must be magnified from 600 to 1200 
times before the human eye can see them. The germ comes 
to maturity in 20 minutes and then divides, so that in 40 
minutes there are four young germs that in 20 minutes more 
will be eight; and in a week billions will be in existence. 

This rate of growth is of course not maintained, but is 
checked by lack of food, by the substances they secrete, by 
temperature, and many other causes; yet they exist in num- 
bers beyond human comprehension, as a single nodule may 
contain more thousands of inhabitants than our largest 
cities. 

They grow and do their work in perfect darkness and are 
killed almost instantly when exposed to the full action of 
the sun's rays. This is due to the actinic and not to the heat 
rays. 

While they are easy to kill in some ways, in others they 
are very resistant, going into a spore or hibernating condi- 
tion which serves to tide the species over a period of dryness, 
famine, or unsuitable temperature, and to preserve alive in a 
hostile environment a sufficient number of individuals until 
favorable conditions return. (22, 1, 5, 4, 34, 55.) 

Hellriegel and Wilfarth in 1886 showed that the tubercles 
were associated with the assimilation of free nitrogen (30, 7) 
and since then the life history of the germs 
HISTORICAL has been worked out by scores of scientists 
such as Atwater in America; Lawes and 
Gilbert in England; Boussingault, Ville, Pasteur, Schlossing, 
and Muntz of France; Nobbe in Germany, and Winogradsky 
of Russia. Their work has been verified at Agricultural 
Experiment Stations all over the world, and the farmer can 



Nitrating the Soils 9 

now utilize this method -of obtaining nitrogen, feeling that 
he is not experimenting, but using established, facts and 
well-known truths. (21, 13, 3, 7, 30, 18.) 

Legumes, such as soy beans, cow peas, vetch, alfalfa, etc., 
form a plant partnership with the nitrogen bacteria that is of 

immeasurable value to agriculture. 
PLANT PARTNERS It is not a parasitic relationship 

where one of the plants is injured 
while the other is benefiited; but it is one of mutual helpful- 
ness. The legume furnishes the home for the bacteria, and 
in its sap, or juice, most of the nourishment upon which the 
bacteria live. The bacteria gain entrance to the roots of 




Seed not 
Inoculated 



Courtesy Armour Fertilizer Works 

RED CLOVER 

Seed Inoculated 
with "Nitragin" 



legumes through the hair roots, causing a very definite tis- 
sue reaction at the point of invasion. Once having gained 
entrance they confer upon the plant immunity from other 
bacteria, as only bacteria of higher virulence than those in 
the nodules are able to enter the roots. (1,5,22.) 



10 University of Southern California 

The nodule, or tubercle, found on the roots of legumes is 
the home of the bacteria somewhat as the ball on the willow- 
twig is the home of the insects within. 
THE NODULES The -nodule itself is an expansion, or 
excessive growth of the cells of the 
legume root, and varies in size from a pinhead to a pea ac- 
cording to the legume it grows upon. During the early stages 
of growth long thread-like sacs, or tubes, force their way 
through the root cells, and the bacteria live in these sacs. 

The nodules are home fertilizer factories where the bac- 
teria take the nitrogen from the air and convert it into solu- 
ble nitrates which pass at once into the plant circulation. 

It is the air IN the soil which the bacteria use, not the air 
above the soil, and the accumulation of nitrogen takes place 
first of all inside the nodule. It is evident, therefore, that the 
soil must be porous so that the air can get down to the root 
hairs, or the bacteria will have no nitrogen to work on. (30, 
7, 9, 14, 22.) 

The permanence of the bacterial life is most important 
and the farmer should note carefully the things that affect 

their continued existence in his soil. While 
LONGEVITY they multiply rapidly, and die with almost 

equal rapidity, permitting the host plant to 
profit by the nitrogen they kave combined into nitrates; yet 
they are after all very persistent and maintain their con- 
tinued existence against great odds. There is only a scanty 
growth of the germs unless free oxygen is present, hence the 
soil must be deeply aerated. Since they feed during their 
growth they are affected by the food the plant feeds on, 
as well as effecting profound changes in the material upon 
which they feed. The soil must, therefore, be adapted to 
the host plant or the sap will not stimulate the growth of the 
germ. The bacteria are live, sensitive plants, requiring free 
oxygen and easily destroyed if contaminated with filth, and 
are, therefore, injured by some forms of organic matter such 
as .too fresh manure, and highly concentrated decomposing 
masses. (30, 27, 10.) 



Nitrating the Soils 1 1 

The nodules are windowless little houses and the bac- 
teria live and work in darkness while unlocking the soil nit- 
rogen, and are easily destroyed by light. Inoculated seed 
should be kept in the dark until used, and protected from sun- 
light as far as possible while planting. 

A drought will not kill the nitrogen bacteria but renders 
them inactive for the time, and thus diminishes the percent 
of nitrogen gained; and a continued drought makes it diffi- 
cult to revive the germs from a dried condition. (19, 26.) 

Every organism, animal or vegetable, has what is known 
as its optimum, or best, temperature at which point it is 
most vigorous; and each has its maximum and minimum 
temperature at which its characteristic activities cease. The 




Seed not 
Inoculated 



Courtesy Armour Fertilizer Works 

COW PEAS 

Seed Inoculated 
with "Nitragin" 



optimum temperature for the nitrogen bacteria is 36.6° C, or 
98° F; although nitrification may proceed in a measure from 
4.4° C, or 40° F to 54.4° C, or 130° F. (12.) The lowering 
of the temperature affects the bacterial activity, yet they 
survive winter freezing, remaining dormant in their little 
nodule houses; but their activities are of no importance be- 
yond keeping the species alive. (41.) This is an advantage 
as no soluble nitrates are produced to be lost by the leach- 
ing of the spring rains. 

Bad soil conditions, and a lack of potash and phosphorous 
for the host plant may starve the bacteria into a degen- 
erative stage of branched and vacuolated forms that do not 
grow or form colonies. (19,20,27.) 



C^ y-*^ 



12 



University of Southern California 



Science does not yet know what different species there may- 
be among the nitrogen bacteria, but it does know that there 

are different types or varieties each adapted 
VARIETIES to its particular legume. Cow peas demand 

one variety, soy beans another, alfalfa still 
another, and so on. 




Courtesy Armour Fertilizer Works 
ALFALFA 
Seed Inoculated Seed not 

with "Nitragin" Inoculated 

Varieties adapted to one legume may be unable to produce 
nodules on another species, and germs that were very active 
when associated with one species of plant may refuse to 



Nitrating the Soils 1 3 

form nodules on the roots of a closely allied species. (54, 
22.) 

By selecting legumes having vigorous growths of tubercles 
many of the most useful varieties have been segregated and 

the breeding of pure germs has 
PURE BRED BACTERIA become a business, a science, 

and as much of an economic 
necessity as the breeding of high-grade cattle. The high-bred 
germs are more vigorous, and therefore more resistant to 
drought, and other unfavorable conditions. 







Courtesy Armour Fertilizer Works 

ALFALFA 
Seed not Seed Inoculated 

Inoculated with "Nitragin" 

They give the quickest and shortest road to success and 
it is always wisest to depend upon pure cultures for inocu- 
lating the seed. 

Most soils are not naturally supplied with the nitrogen 
bacteria; and there are other soils in which they are already 
present but not in sufficient quantities, 
NOT PRESENT or of good grade. It is like a man hav- 
IN MOST SOILS ing some mongrel range cattle on his 
ranch. He must invest in blooded stock 
in order to bring his ranch up to th.e grade necessary for 
making the most money. The clover bacteria were not orig- 
inally found in Illinois soils, causing a failure of red clover 
under otherwise normal conditions. Alfalfa was pro- 
nounced a failure for years in Illinois because there were 
no alfalfa bacteria naturally in the soil; but the crop is now 
a success wherever the bacteria have been introduced. The 



14 University of Southern California 

soy bean bacteria did not exist in Connecticut soils and had 
to be introduced; and the investigations made in many other 
states give additional illustration of this fact. (53, 54, 49.) 

Only such plants as develop tubercles are able to increase 
the amount of nitrogen in their tissues. No leguminous 

plant is able of itself to secure nitrogen 
NO NODULES, from the air, but each legume must be 
NO NITROGEN provided with the particular variety of 

bacteria which has the power to live 
upon its roots and gather nitrogen from the soil atmosphere. 
The marked effect of inoculation is seen on the growth, 
color, and composition of the plant even though only half 
a dozen large nodules form on the roots. The greater the 
number of the nodules the better the growth. Plants with- 
out nodules show no increase; those with a moderate num- 
ber show a slight increase; while those with abundant 
tubercles grow luxuriously and show the largest increase 
in nitrogen. (23, 19,20.) 

There is no time when plants are so susceptible to injury 
by unfavorable soil conditions as in the early period of their 

growth. Plants sprout readily and for 
THE NITROGEN a short time grow, vigorously, then the 
HUNGER STAGE vigorous growth ceases and the plant 

seems to be suffering for lack of food. 
This is the nitrogen hunger stage, a period in which the plant 
not inoculated has used up all the nitrogen in its seed; and 
unless the seed was inoculated the baby roots have to begin 
searching through the soil in all directions for the nitrogen 
the plant must have. In the meantime the top growth has to 
wait and starve until the supply has been found and the nitro- 
gen begins to come to the plant. The uninoculated plant leads 
a struggling existence until supplies of soluble nitrogen have 
been found in the soil. If the seed has been inoculated, as 
soon as it sprouts and the roots begin to grow the bacteria 
begin to supply the nitrogen which the baby plant at once 
assimilates, giving a vigorous growth from the start, and abso- 
lute protection from the nitrogen hunger. (53, 46.) 



Nitrating the Soils 15 

THE SOIL 



Primitive methods have led to the belief in lack of soil 
fertility. The record of the human race in the past has been 

one of ruined lands, in Palestine, in southern 
FERTILITY Europe, in Russia, and in the eastern part 

of the United States. The slogan of the 
present is increase the fertility of the soil. We must not 
be satisfied with a temporary system of agriculture in 
which the available food steadily decreases; but we must 
demand a permanent system in which all the available plant 
food is perpetually maintained. It will not do to drift with 
the tide waiting for something to turn up. We must be 
alert to seize every discovery of science and utilize it. We 
must know the inner mysteries of the soil as we know the 
inner mysteries of plant life. 

Soil fertility is the crop producing power of a soil, under 
the best conditions; and this fertility depends largely upon 
three factors: first and most important, the physical charac- 
ter: second, the bacteriological character: and last the chem- 
ical composition. 

The soil has two functions; first, it furnishes a home, a 
mere lodging place for the plant in which it lives and moves 
and has its being; second, it furnishes food for the nourish- 
ment, growth, development, and maturing of the plant. If 
the physical condition of the soil is poor, or the chemical 
composition unusual, no amount of inoculation will pro- 
duce crops equal to those grown on fertile soils. Maintain- 
ing the fertility of the soil means that there shall be pre- 
served within the soil sufficient amounts of soluble plant 
food of the various kinds necessary to produce maximum 
crops. The growing of inoculated legumes is absolutely es- 
sential for maintaining the nitrogen supply, and necessary 
as a part of any economic system which shall maintain the 
fertility of the soil; of any system that will make a poor 
soil fertile, and keep a good soil fertile. (54, 26, 17, 39, 6.) 




U. S. Dept. Agriculture. 



Hairy Vetch and Rye Growing Together 



Nitrating the Soils 1 7 

The absolute essentials in the growing of crops are: I, 
the seed; 2, the soil, or home and lodging place; 3, the food; 

4, the drink, or moisture; 5, 
ABSOLUTE ESSENTIALS the heat; 6, the light; 7, free- 
dom from weeds; 8, freedom 
from disease. 

Any one of these factors may limit the yield of crop. Poor 
seed is poor economy. Proper soil conditions are as essen- 
tial to the life and activity of the bacteria as they are to the 
growth of the plant. 

The inoculation of the seed is only one step towards suc- 
cess, and no matter how carefully carried out, will fail if 
the other things just as essential are not looked after. 

Each type of soil is specially adapted to specific crops and 
this adaptation should be closely studied. There should be 

reason and moderation in all 
CROP ADAPTATION things. Some want to grow alfalfa 

and other crops on soils not 
adapted to them, by applying bacteria, and then complain 
of lack of success. Such ideas, and such practice are not a 
part of intelligent farming. 



The quantity of active nitrogen furnished the plant de- 
pends more upon the physical condition of the soil than on 
its nature and corhposition. Nitrification is a 
AERATION process of oxidation as well as combining 
nitrogen, and the soil must contain oxygen. 
As all the nitrogen obtained must come from the air in the 
soil, the soil must be porous so that the atmosphere may 
penetrate it. The deeper the air penetrates the soil the 
deeper the nodules will be found and the greater the quantity 
of nitrogen obtained. Thorough cultivation of the soil and 
DEEP PLOWING are necessary to thoroughly aerate it. 
This aeration also reduces in number certain other kinds of 
soil bacteria that are inimical to the nitrification process. 
(19,42,6.) 



18 Universii'^ of Southern California 

The number of bacteria in a soil is closely related to the 

moisture conditions, and even slight differences in the 

amount and kind of moisture present may read- 

MOISTURE ily cause differences in crop production and in 

bacterial activity. 

The soil must not be too wet, or water-logged; and it 
must not be too dry. There should be a good supply of 
water vapor and film, or hygroscopic water, maintained by 
good capillary conditions. If the voids are filled with water 
the air cannot penetrate the soil. The root hairs feed in 
the films of moisture clinging to the soil particles, and this 
supply is kept replenished by capillary action drawing up 
water from below. (19,20, 11.) 

The number of bacteria in soils decreases as the temperature 
is lowered, being practically at a minimum when the soil is 

frozen. When the soil temperature does 
TEMPERATURE, not go far below the freezing point the 

mineral matter in the film water may 
keep it from freezing and bacteria may multiply to some 
extent, keeping the species alive without hibernation. Thor- 
ough cultivation of the soil admits air, warming the soil 
as well as draining off excess water. The great difficulty in 
cultivation is that plows and other implements do not go 
deep enough. This has led to the introduction of plowless 
agriculture, or loosening up the soil by means of explosives. 
As nearly all legumes will send their roots very deep if per- 
mitted by the soil conditions the use of explosives is of 
special benefit when inoculating with nitrogen bacteria. 
(7, 12, 6.) 

The use of explosives sets free plant food; plows deep 
without mixing the subsoil with the top soil; admits oxygen 
of the atmosphere to the organic matter 
THE USE OF in the soil hastening decomposition; ad- 
EXPLOSIVES mits nitrogen of the atmosphere to the 
roots, promoting bacterial nitrification; 
makes all the soil available by fining it; breaks up hard 
pan; makes a reservoir for water; warms and dries the 
soil; saves the rain by taking it into the soil; prevents evap- 



Nitrating the Soils 19 

oration and conserves moisture; permits the roots to go 
deep down into the soil; makes the moisture of the subsoil 
available; makes the plant food in the subsoil available; and 
converts subsoil into fertile soil, deepening the feeding zone 
of the roots. (74.) 

PLANT FOODS 

Crops are not made out of nothing but are built up from 
food elements just as a building is made of wood, iron, brick, 
stone and mortar; for without materials nothing material 
can be made. 

A few simple facts should be kept in mind, viz: that 95 
per cent of most plants consist of carbon, hydrogen, and 
oxygen; and that the remainder consists mainly of nitrogen, 
potassium, and phosphorous; with minute quantities of iron, 
lime, magnesium, silica, etc. 

There is no market value to the carbon which the plant 
inhales through its leaves; or to the hydrogen and oxygen 

which they obtain from water; or 
NO MARKET VALUE to the calcium, magnesium, iron 

and sulphur because only minute 
amounts are required and because they are practically 
present in ALL SOILS in sufficient quantities for plant 
growth. 

There is a high market value to nitrogen, potash, and 

phosphorous because all plants re- 

A MARKET VALUE quire considerable quantities, and 

they are naturally present in soils 
in rather limited quantities. 

Plants require balanced rations as much as cattle, and 
adding nitrogen to a plant starv- 

BALANCED RATIONS ing for potash or phosphorous 

will do no good and only tends to 

still further unbalance the food supply. 



20 University of Southern California 

Potash is obtained largely from the mineral deposits of 
potassium salts, from wood ashes, and should also be obtained 

from the inexhaustible supplies of sea 
FOOD SOURCES kelp. Phosphorous is obtained from 

rock phosphates, slag phosphates, bone 
meal, etc. 

Small quantities of nitrogen oxides are formed by electrical 
discharges through the air and are washed down by the rains. 
Organic nitrogen exists united with carbon, hydrogen, 
oxygen and other elements in the form of partially decayed 
vegetable and animal matter, but is insoluble in that form 
and unavailable for plant food. It is contained in ammonium 
salts, in dried blood, and .cottonseed meal, and other sources. 

The principal source, however, has been sodium nitrate, 
also known as niter, and Chili saltpeter, the main supply 
coming from the deserts of Taramaqual in Chili. 

Sodium nitrate contains 15 to 16 per cent of nitrogen; am- 
monium sulfate 20 to 21, and dried blood 12 to 15 per cent. 

The manufacture of calcium nitrate by uniting atmos- 
pheric nitrogen with lime by means of powerful electrical 
discharges was started abroad a few years ago, but this 
supply is now shut off by the war. 

The cost is excessive and no farmer can afford to purchase 
a pound for general farming. Only market gardeners who 

take off several crops of high 
DISADVANTAGES OF market value a year, or those 
MINERAL NITRATES raising special crops like oranges 

and lemons can afford to use the 
commercial forms of nitrogen fertilizers. 

Mineral nitrates are easily lost because they are very solu- 
ble, and if left in the soil in the fall or formed during the 
winter may be largely lost before spring by percolating 
waters unless the land is covered by a crop that will take 
them up. 

It is often difificult and expensive to apply them at just the 
proper time, when the plant, tree, or crop needs them most. 




U. S. Dept. Agriculture. 

Roots of Peanut Vine, Showing the Value of this Plant as a Nitrogen 
Gatherer. The Nodules on the Roots are formed by the Bacteria 
which collect the Nitrogen. 



22 University of Southern California 

Very large quantities of nitrate of soda are necessary to 
bring crops, from barley to oranges, upon a par with those 
supplied by legumes. 

The crop uses only the nitrogen and does not need the soda, 
and the continued use of nitrate of soda may have an in- 
jurious effect on the soil, even to producing an alkali condi- 
tion. 

With mineral nitrates one does not get the benefit of 
added humus and organic matter as when the legumes arc 
plowed under and decompose in the soil. (49, 42, 45.) 

Nitrogen is removed frorrnthe soil not only by crops 
grown, and by drainage waters, but also by the blowing oflf 
of the surface soil; and by the action of denitrifying germs, 
and the losses this way may be several times the amount 
used by the crops. 

If any question pertaining to the science and practice of 
agriculture is settled it is this — that the atmosphere is the 
most economical source of nitrogen 
NITROGEN FROM for all general farming. 
THE AIR The atmosphere consists of a 

mixture — not a combination — of 79 
volumes of nitrogen to 21 of oxygen; or by weight, 77 per 
cent of nitrogen to 23 of oxygen. In the air nitrogen is inert, 
combining with nothing, and only serving to dilute the oxygen. 
The atmosphere gives an inexhaustible supply, for all that is 
drawn from it returns again in the cycles of plant and ani- 
mal life. It has been estimated that if the population of the 
earth was 1000 million it would take 3800 years for their 
respiration to use up one per cent of the oxygen of the air. 
if none was returned in the meantime; and there is about four 
times as much nitrogen to draw from as there is oxygen. 
There are about 75 million pounds of nitrogen resting on 
every acre of soil, pressing down upon it nearly 15 pounds 
per square inch, or more than a ton to the square foot. The 
air over each acre of land contains sufficient nitrogen for 
a hundred bushel crop of corn every year for 40,000 years; 
and owing to the cycle of life from soil to plant, from plant 
to animal, and from animal back to the soil, the supply is per- 



Nitrating the Soils 



23 



manent. This free and inexhaustible supply cannot be used 
by any plants except legumes, and they cannot use it unless 
the nitrogen gathering bacteria are present. (54, 50, 23, 25, 34, 

42, 55.) 




U. S. Dept. Agriculture. 
Roots of Soy Beans, Showing Nodules 



Varro wrote before the Christian era that lupines were 
plowed into a poor soil in lieu of manure; but agriculture has 
had to wait for centuries to know why 
THE LEGUMES and how the lupines fertilized the soil. 

All plants which bear their seed in a 
capsule or pod, such as clover, alfalfa, peas, beans, vetch, 
peanuts, etc., are known as legumes. 

The legume itself has no power to fix nitrogen. This 
power rests wholly with the bacteria in the nodules on the 



24 University of Southern California 

roots of the legume, which do have the power to take the 
free nitrogen from the air and unite it with othe' elements 
forming nitrates which are dissolved in *b(: juices of the 
legume. 

The farmer secures the presence of these bacteria by in- 
oculating the seeds of the legume before planting them. A 

legume that has no. bacteria nodules is a soil robber, for 
inoculated legumes grow just the same as other plants and 
must get their nitrogen from the soil the same as non- 
leguminous plants. 

Each legume must have its own particular variety of bac- 
teria. In fact one of the most dominant causes of failure or 
unsatisfactory growth of some of the most valuable legumes 
is the absence of the proper nitrogen gathering bacteria. 

Today the farmer can get all the germs he wants and sow 
them with the legume seed, thus taking a most important 
step towards insuring a perfect stand and stocking the soil 
with nitrogen. 

It is easy to see if the bacteria are present, for all that one 
has to do is to pull up a few plants and see if the nodules are 
there on the roots. Where the plants are sparsely infected 
the individual nodules develop to an enormous size, but few 
in number. Where the soil is well infected the individual 
nodules are much smaller and more numerous. 

Legumes are deep rooted plants and require thorough 
and deep tillage of the soil. This increases their value to 
the farmer for it carries nitrification deep down, fertilizing 
the soil to depths that no other method can. 

As the legumes approach maturity the nitrogen is largely 
absorbed from the tubercles and stored in the tops and roots 
of the host plant; then if the legumes are plowed under all this 
nitrogen, together with millions of the germs are distributed 
in the soil. They should be plowed under before the crop 
fully matures so that thorough decomposition may quickly 
occur. (53, 54, 49, 2, 4, 28, 33, 57, 59.) 



Nitrating the Soils 25 

Nitrogen bacteria cannot live in an acid medium and are 

absent from acid soils. The decay of leaves and the decom- 
position of organic matter usu- 
NONE IN ACID SOIL ally produces acids that kill oflf 

the little workers and put an end 
to their usefulness. Even soils which overlie limestone may 
be acid in their first foot or two. The soil should be tested 
with litmus, or other reagents, to be sure that it is not acid. 
(1,5.) 

There is a class of bacteria that are denitrifiers setting 
soil nitrogen free again. They do not live in nodules, but 
are abundant in manure heaps and in all 
DENITRIFIERS de(composing heaps, and jdimimsh rap- 
idly when the manure is well rotted. 
Only well-rotted manure should be used where legumes are 
planted, and then only in limited quantities. Denitrifying 
germs are particularly active in soils carrying a limited 
amount of air, and in water-logged soils. These facts again 
emphasize the necessity for thoroughly and deeply culti- 
vating the soil. (1, 5.) 

If no alkaline element like lime, potash, or magnesium is 
present in the soil no nitrate can be formed. The lime sup- 
plies the base for uniting with the 
LIME NECESSARY nitrogen and oxygen in forming the 
soluble nitrates. Its presence is 
necessary also to neutralize any acid in the soil. Old air 
slacked lime, fine ground limestone, and marl are the most 
economical forms to use. Fresh burned lime, or fresh 
slacked lime are not advisable as they tend to attack and 
destroy the organic matter in the soil, or "burn the land." 
Fifty-six pounds of lime will furnish 74 pounds of perfectly 
dry slaked lime. The amounts required vary widely accord- 
ing to local conditions. In some soils 1000 pounds of lime- 
stone per acre is ample, in others three tons per acre are 
required. 

Lime helps to conserve the moisture and aid in carrying 
the bacteria through a period of drought. It is also of indi- 



26 Univefsiiy of Southern California 

rect benefit in unlocking potash and phosphorous that are 
present in the soil but unavailable. (54, 19, 49, 29, 32, 56, 75.) 

All soils are not adapted to the same legumes. One soil 
may be specially adapted to beans, producing a large crop, 
developing quantities of nodules and fix- 
VARIETIES OF ing an abundance of nitrogen, yet the 
LEGUMES same soil may not support alfalfa or 

other species of legumes nearly as well. 
Fortunately there are a large number of legumes that have 
been bred to a high state of perfection, together with their 
specific bacteria, giving an assortment covering nearly every 
peculiarity of soil and climate. 

Alfalfa, the queen of forage plants, is a muscle-building 
feed, while corn is a fattening and heating feed, and to- 
gether they make an excellent ration for any animal on the 
farm. Alfalfa roots go down to great depths, 12 to 20 feet 
being common; while 65 feet has been noted in California. 
This deep rooting habit enables it to stand drought, and is 
of special value because large quantities of mineral plant 
food are brought up from the depths. (40,44,47.) 

There is a world-wide demand for Peas and Beans as food 
for the human race, and they can also be readily converted 
into milk, pork, mutton, beef, and other cash money prod- 
ucts. (58, 60.) 

The Cowpea and the Soy Bean will grow upon land too 
poor to grow anything else. They are used in the rotation 
of crops to maintain fertility; and as a supplementary feed 
to balance other rations in feeding animals. They may be 
sown with grain and corn or used after oats as a fertilizer 
or catch crop, or as an orchard cover crop cultivated during 
the season and then pastured of? with hogs. Inoculated 
cowpeas contained 4.09 to 4.33 per cent of nitrogen jn their 
tops and 1.42 to 1.53 per cent in the roots, while those not 
infected contained only 2.32 to 2.69 per cent in the tops and 
.88 in the roots. (54, 35, 48, 51, 61, 62, 64, 72.) 

It is often difificult to get at catch of Clover on new land be- 
cause its bacteria are not present in the soil, but a good 
catch or stand is secured if the clover seed is inoculated. 



Nitrating the Soils 



11 



Clovers make potash and phosphoric acid in the soil available; 
protect the soils from blowing and washing; change loose 
sand into a compact loam with greater mosture holding capac- 
ity; tind make stifif clays more open and friable, allowing 
better aeration. They make good cover crops for fields in the 
winter, from corn to cotton. (15,16,63,66,71,73.) 



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U. S. Dept. Agriculture. 
Peanuts Growing in the Alleys Between Rows of Corn 



The common, or summer vetch is extensively used on the 
Pacific coast and in the southern states as a winter hay crop 
being sown with oats, rye, or wheat; and in the citrus groves 
as a winter green manure crop. 

The winter, or hairy vetch is more resistant to cold than 
any other annual legume grown. It is used as a green 
manure and cover crop on tobacco lands and in orchards. 
(69, 70.) The lupines make a rank growth and are exten- 



28 University of Southern California 

ively used in Germany for putting humus and nitrogen into 
sandy soils. 

The sanfoin, or esparsette is similar to the clovers in some 
respects. It may be sown with any of the grains as a Hurse 
crop, and later cut for hay or turned under for humus and 
nitrogen. One of the most valuable annuals is the serra- 
della as it remains green under the snow in winter, giving 
winter pasture. It is also valuable for recovering sandy 
wastes, for cover and nurse crop, for feeding stock, and as a 
green manure being plowed under in the spring to be fol- 
lowed by potatoes, corn, or cereals. 

Nitrogen germs will not develop on the roots of non-legu- 
minous crops and it is useless to inoculate their seed. They 
must be furnished with nitrogen by 
NON-LEGUMINOUS the legumes. Cowpeas, crimson 
CROPS clover, vetch, etc., are inoculated 

and planted between the rows of 
corn or cotton, and plowed under after the harvest. The 
clovers, sainfoin, serradella, etc., are often sown with wheat, 
oats, rye and other cereals, and the whole crop is sometimes 
turned under as a green manure. Alfalfa, clover, vetches are 
inoculated and planted between the rows of orchards and 
small fruits and plowed under for the humus and nitrogen. 
Some legumes, like the black-eyed bean, peanuts, etc, are 
made a source of income while the young orchard is grow- 
ing. Legumes do not make a sod difficult to work and may 
be planted ahead of crops such as hops, cotton, tobacco, as- 
paragus, potatoes, and grain, or in fact of any crop that needs 
nitrogen. 

The benefits derived from inoculating legume seed with the 
nitrogen bacteria are threefold: 1, it increases the crop; 2, it 
increases the food value of the crop; 3, it 
BENEFITS increases the fertility of the soil. Evidence on 
these points is readily obtained from any of the 
many agricultural stations. It is well known that inoculated 
crops sprout quicker, grow faster, have a darker, richer green 
color, and larger blossoms. Bacterial nitrogen is better dis- 
tributed through the soil than mineral or organic nitrogen. 



Nitrating the Soils 29 

and two tons of clover or cowpeas plowed under may have 
greater power to liberate plant food than 20 tons of old, 
inactive matter in the soil. Bacteria can put from 150 to 200 
pounds of available nitrogen in each acre, where the legumes 
are properly used; and this is worth from $25 to $30 per acre 
according to the market value of nitrates. In New Jersey the 
increase in dry matter by inoculation was, for alfalfa 500 per 
cent; beans 75 per cent; while cowpeas more than doubled. 
(24.25.) The University of Illinois says: By proper inocula- 
tion we have grown a crop of alfalfa which contained as high 
as 17 times the quantity of nitrogen as was contained in a 
crop grown without inoculation but otherwise under exactly 
the same conditions. (52.) The same authority says $1 of 
lime made more than a $10 increase per acre in alfalfa hay, 
and $4 of phosphorus made an additional increase of hay, 
while the presence or absence of alfalfa bacteria made the 
crop a success or failure respectively. (50.) Canada field 
peas inoculated by pure culture supplied more than seven 
times the amount of nitrogen furnished by those not inocu- 
lated. 

The increase in corn in Iowa was from 52 to 68 bushels, 
and in oats from 33 to 55 bushels. (19) In Alabama the 
inoculation increased the yield of hairy vetch 89 per cent, of 
Canada field peas 138 per cent, and of crimson clover 146 per 
cent. (2.) In Arkansas, legumes were grown and turned 
under on cotton land and corn land with the following results: 
Cowpeas gave 1335 pounds of seed cotton per acre; soy beans 
gave 1448 pounds; and velvet beans gave 1550 pounds of seed 
cotton; the corn land§ gave with the cowpea 37 bushels per 
acre; and with the soy beans 42 bushels of corn per acre. (4.) 

Protein is the general name for a series of organic com- 
pounds that contain nitrogen in addition to oxygen, carbon 

and hydrogen. One group consists of the 
INCREASE IN final nitrogenous organic compounds called 
PROTEIN PROTEIDS, which constitute the FLESH, 

(not the fat) and VITAL ORGANS of 
animals, and the protein of mature plants. The number of 
proteids is very large, and all contain nitrogen, usually about 



30 University) of Southern California 

16 per cent, and some of them also contain phosphorous and 
sulfur. The high cost of living is already calling attention to 
the special value of peas and beans, as they contain as much 
protein as meat, and the best way to insure this supply is by 
inoculating the seed. The more protein there is in the crop, 
the more beef it makes when fed to stock. 

Soils are never so rich but that their quality may be im- 
proved, or so poor but that they may be made to produce 

good crops. Where there is a de- 
BENEFIT TO THE SOIL ficiency of humus or decompos- 
ing organic matter in the soil a 
green manure crop of inoculated legumes should be plowed un- 
der, increasing the fertility of the soil; increasing the yield and 
food value of succeeding crops; restoring fertility to land that 
now produces little or nothing; and by stocking the soil with 
nitrogen increasing the CASH VALUE OF THE FARM. 

The masses of the fine roots of the legumes penetrate and 
hold the soil together during the heavy winter rains and 
prevent surface washing, saving the fertile top soil. They also 
regulate the moisture supply, and modify the ill effects of 
extreme temperature. They keep the soil in good physical 
condition, the turned under legumes binding together loose 
sandy soils, loosening up stiff clay soils, and making loams 
loose and friable. 

They are a safeguard against injury to fruit at harvest time. 
They insure against the wearing out of the soil. 

Plants not only secrete food but excrete waste material, 
poisoning the soil with these toxins, and finally checking their 
own growth. Some crops are not in- 
CROP ROTATION jured by the toxins left by preced- 
ing crops in the soil; other crops are 
injured; and a few thrive. The secret of successful crop 
rotation lies in selecting a crop that will remove or neutralize 
the toxins left by the preceding crop. The object of rotation 
is to preserve the fertility of the soil; to maintain its good 
physical condition; and to put back ALL the plant food re- 
moved from it. 



Nitrating the Soils 



31 



It helps to maintain the organic matter in the soil, and is 
aided by the use of all farm manures, and a liberal use of 
green manures. Rotation, however, is not enough, as for 
example in Ohio a five years' rotation of corn, wheat, clover 
and timothy did net secure sufficient nitrogen for maximum 
crops. The rotation must contain legumes. It is not assumed 
that the bacteria can replace other plant foods, or do away 
with the proper cultivation of the soil; but inoculation with 
the nitrogen bacteria is the secret of success in sticcessful 
crop rotation. 





Courtesy Armour Fertilizer Works 
SOY BEANS 



Seed inoculation is not a new discovery, and there is noth- 
ing mysterious about it. It is admitted by all authorities that 
it can be successfully performed by any 
NO MYSTERY careful farmer who will take the neces- 
sary time and pains. IT IS NOT A 
CURE-ALL, and no sensible man will claim it as such; it 
does not take the place of potash or phosphorous; sweeten 
sour or acid soils; or remove the necessity of thorough culti- 
vation; but it can double the yield of crops where all the 
other conditions given are favorable. 



32 University of Southern California 

The best method is to inoculate the seed by treating it with 
a proper culture of the special germ adapted to the legume 

before planting. The most sci- 
INOCULATE THE SEED entific method is to obtain a 

pure culture, for specialists 
have succeeded in breeding strong, healthy, vigorous germs 
which can be sent by mail to the farms and orchards; and 
are as clearly an economic necessity as pure-bred cattle 
or pure-bred sugar beets. The cultures should be fresh, as 
they then contain a larger number of active organisms and 
are better for inoculating than old cultures. 

Use only the best seed, and get them free from weeds. 
Poor seed is worse than none at all; and bacteria are not 
weed killers. 

Follow the directions of the parties you buy the germs 
from, only seeing that the seed is thoroughly wet; and then 
spread it out to dry where it will not mould or sprout, or 
lose its vitality by exposure to sunlight; or be subject to any 
of the conditions mentioned that weaken or destroy the bac- 
teria. Remember especially that the bacteria are minute, 
delicate plants that live and work in the dark, and should no 
more be exposed to direct sunshine than a photograph plate. 
They should be mixed with the seed when the sun is not 
shining, or in the evening; and should be planted mornings 
and evenings, unless the sky is clouded. Be sure of your 
dealer, as it has been found in a few instances that some 
cultures did not contain the nodule-forming germ at all, a 
mistake easily made by anyone not a specialist, as there are 
soil bacteria that produce colonies VERY SIMILAR in 
appearance to the tubercle-forming ones. (15, 26, 23.) 

Tubercle-forming bacteria will disappear from some soils 
in a few years if the legume upon which they grow is not 
grown occasionally; while in other soils 
PERMANENCE they seem to remain, becoming nor- 
mally present. Bacteria growing in soil 
richly stocked with organic nitrogen lose much of their power 
to fix new nitrogen, and the nodules seem to dwindle away 



Nitrating the Soils 33 

and lose their peculiar function, seeming to follow the gen- 
eral law that unused organs suffer atrophy. 

Inoculation is a benefit wherever nitrogen is needed in the 
soil; where the soil has not previously borne legume crops; 
TNOCTIT ATTON wherever the legumes previously grown 

AN ADVANTAGE showed only a few nodules, or a weak 
growth of crop; where the legumes to 
be grown belong to a species not closely related to the one 
previously grown on the same soil. If you have bad spots 
in a field, take good, sweet, inoculated soil from the same 
field, and never from some other field, and spread it on the 
bad spots. 



Every teacher knows that it is easier to teach 20 men what 
is good to do than to persuade one man to do it. Be the one 

man in your district to do the right 
CONTROLLING thing, and that is to find out for 

LOCAL CONDITIONS yourself if there is any deficiency 

of any element in your soil; and 
to prove the benefit of all new material by means of test 
plats. TEST PLATS ARE A NECESSITY ON EVERY 
FARM; and are far better than any analysis, chemical or 
physical. They give the prudent method and the cheap- 
est method of checking results. The one-twentieth of an 
acre is a handy size. Plant one plot with the legume with- 
out using any germs or fertilizer of any kind; on another 
plant the legume and use inoculated seed, without using 
potash and phosphorus; on another use inoculated seed and 
potash and phosphorous. Each plot should be treated with 
lime to neutralize any acidity in the soil. Be careful that 
water from the inoculated ground does not drain onto plats 
not inoculated and thus make comparison impossible. When 
full grown cut an equal area from each plat and weigh 
each separately and compare; but do not trust the eye alone, 
as a 25 per cent increase may not show unless you weigh. 
Dig samples of roots from each plot, going deep enough to 
get the entire roots; wash carefully until the roots are white; 



34 University of Southern California 

put the bunches of roots into separate glasses and let the 
roots float apart, noting the form, size and number of the 
nodules. Each nodule means so much nitrogen for the land. 
Do the work carefully, as the nodules strip ofiF easily and 
may be lost, especially where small but numerous. 

Normally, seasonal and climatic conditions vary, and 
changes in local temperatures and in moisture are constant 
and one must make allowance for them in his methods of cul- 
tivation. Use test plots for checking seed, crops, fertilizers, 
and dififerent methods of cultivation on your own soil. Inves- 
tigations of local peculiarities are not experiments but invest- 
ments, a guide towards success, and a protection against loss. 
Trifles noted may give success, and SUCCESS IS NO 
TRIFLE. Test and know with your own knowledge before 
condemning anything new in agriculture. 

The dangers of inoculation by soil transfers are not imag- 
inary but clearly established at many of the state experiment 

stations, and it is now considered 
SOIL TRANSFERS folly to try such a haphazard method. 

It may, and has, transferred plant 
diseases, noxious weeds, and insect pests. The cost of trans- 
ferring 400 to 500 pounds per acre from one locality to an- 
other is large, and the task is laborious. Many bacteria are 
killed by the sunshine during the transfer, and the germs 
are often weak and lack strength to penetrate the roots of 
the legumes. The inoculation with pure cultures leads to 
better results. (30.) 

Success is a matter of brain, not brawn. Have faith in the 
investigations at experiment stations and do not condemn the 
principle, but study the methods that 
PRECAUTIONS lead to success. The dealer can only 
guarantee the purity and vigor of his 
bacteria, he cannot force the farmer to guard himself against 
failure caused by not closely observing the other factors of 
success. Most failures come from neglect to follow directions. 
Do not open the cultures until ready to use. Use them only 
for-the crop and acreage as directed. Sow the treated seed as 



Nitrating the Soils 35 

soon as possible. Do not try to keep some over for future 
use, as they drj' out, and a too long dried condition reduces 
vigor. Use fresh vigorous cultures, and keep the germs in 
a cool, clean, dark place such as a cellar. Do not let treated 
seed come in contact with commercial fertilizers. Do not 
spread seed in the sun to dry. Do not plant the seed' when 
the sun is very bright, or hot. Plant on a rainy or cloudy 
day, or in the morning or evening. Do not use on an acid 
soil, but neutralize first with lime. See that the soil contains 
enough potash and phosphorous. See that the soil is well 
aerated, well drained, and warm. See that the crop is 
adapted to your soil, and your local climatic conditions. See 
that foul grass and weeds are kept out. Do not leave things 
to your hired help. Success lies in yourself, for to him that 
hath gumption big crops shall be given. 

REFERENCES. 

1. Agricultural Bacteriology. Lyon & Fippin. Macmillan. 1909. 

2. Alabama Agr. Exp. Sta. — Southern burr clover. Bull. 165. 

3. Archives des Sciences biologiques, Vol. III. 

4. Arkansas Agr. Exp. Sta. Legume manuring. Bull. 58. 

5. Bacteriology. Jordan. Saunders Co. 1908. 

6. California Soils. Bailey. Lmiv. S. Calif. Press. 1914. 

7. Centralbl. f. Bakt. 1887. 

8. Centralbl. f. Bakt. 1897. 

9. Centralbl. f. Bakt. 1900. 

10. Centralbl. f. Bakt. 1904. 

11. Centralbl. f. Bakt. 1909. 

12. Centralbl. f. Bakt. 1910. 

13. Chimie Vegetale et Agricole. — Berthelot. 

14. Delaware Agr. Exp. Sta. Tubercle bacteria. Bull. 73. 

14. Delaware Agr. Exp. Sta. Tubercle bacteria. Bull. 78. 

15. Delaware Agr. Exp. Sta. Crimson clover. Bull. 86. 

16. Delaware Agr. Exp. Sta. Crimson clover. Bull. 89. 

17. Dry farming. Widtsoe. Macmillan. 1913. 

18. Hellriegel — "LTntersuchungen uber die Stickstoffnahrung der Gramineen 

und Leguminosen.'' — Zeitscher, des Vereins fur Rubenzuckerin- 
dustrie .d, D. R. Nov. 1888. 

19. Iowa Agr. Exp. Sta. — Soil bacteriology. Bull. 4. 

20. Iowa Agr. Exp. Sta. — Soil bacteriology. Bull. 5. 

21. Maze. — "Fixation d I'azote libre par le bacille des nodosites de 

legumineuses. Inst. Pasteur. Vol. I. 0897. 

22. System der Bakterien. Jena. 1897. Migula. 

23. Michigan Agr. Coll. — Bacterial activity in the soil. Bull. 16. 



36 University of Southern California 

24. New Jersey Agr. Exp. Sta. Nitrate of soda on crops. Bull. 16. 

25. New Jersey Agr. Exp. Sta. Atmospheric nitrogen in the soil. Bull. 

180. 

26. Oklahoma Agr. Exp. Sta. — Soil inoculation. Bull. 68. 

27. Oklahoma Agr. Exp. Sta. — Soil inoculation. Bull. 69. 

28. Oregon Agr. Coll. — Green manure crops. Bull. 120. 

29. Ohio Agr. Exp. Sta. — Liming the soil. Bull. 159. 

30. Pesn. State Coll. x\gr. Exp. Sta. — Commercial cultures for legumes. 

Bull. 78. 

31. Rettger— Jour. Biol. Chem. 1908. -4. 

32. Rhode Island Agr. Exp. Sta. — Lime, nitrogen and soda. Bull. 47. 

33. Rhode Island Agr. Exp. Sta. — Legumes. Bull. 49. 

34. Rhode Island Agr. Exp. Sta. — The nitrogen problem. Bull. 50. 

35. Rhode Island Agr. Exp. Sta. — The soy bean. Bull. 92. 

36. Soils. Hilgard. Macmillan. 1911. 

37. Soils. Fletcher. Doubleday. 1910. 

38. Soil Fertility. Hopkins. Ginn Co. 1910. 

39. Soil Management. Lyon & Fippin. Macmillan. 1909. 

40. South Dakota Agr. Exp. Sta.— Alfalfa. Bull. 94. 

41. Studien uber de Bakterienorfla des Ackerbodens, etc. Berlin. 1903. 

42. Texas Agr. Exp. Sta. — Active nitrogen in the soil. Bull. 7. 

43. Univ. Calif. Agr. Exp. Sta. Annual Report. 1913-1914. 

44. Univ. Calif. Agr. Exp. Sta. Alfalfa. Circular 87. 

45. Univ. Illinois Agr. Exp. Sta. — Commercial fertilizers. Circular 129. 

46. Univ. Illinois Agr. Exp. Sta. — Plant food and ^oil fertility. Circular 

155. 

47. Univ. Illinois Agr. Exp. Sta. — Alfalfa. .Circular 4. 

48. Univ. Illinois Agr. Exp. Sta. — Cowpea and soybean. Circular 5. 

49. Univ. Illinois Agr. Exp. Sta. — Soil investigations. Circular 64. 

50. Univ. Illinois Agr. Exp. Sta. — Soil investigations. Circular 68. 

51. Univ. Illinois Agr. Exp. Sta. — Cowpea and soy bean. Circular 69. 

52. Univ. Illinois Agr. Exp. Sta. — Soil investigations. Circular 72. 

53. Univ. Illinois Agr. Exp. Sta. — Inoculation of legumes. Circular 86. 

54. Univ. Illinois Agr. Exp. Sta. — Nitrogen bacteria and legumes. Bull. 

94. f 

55. Univ. Wisconsin Agr. Exp. Sta. — Nitrates in soils. Bull. 85. 

56. U. S. Dept. Agr. Farmers' Bull. — Liming of soils. No. 77. 

57. U. S. Dept. Agr. Farmers' Bull. — -Beans and other legumes. 121. 

58. LT. S. Dept. Agr. Farmers' Bull.- — Canadian field peas. 224. 

59. v. S. Dept. Agr. Farmers' Bull.- — Leguminous crops for manuring. 

278. 

60. U. S. Dept. Agr. Farmers' Bull. — Beans. 289. 

61. U. S. Dept. Agr. Farmers' Bull. — Cowpeas and soy beans. 309. 

62. v. S. Dept. Agr. Farmers' Bull.— Cowpeas. 318. 

63. U. S. Dept. Agr. Farmers' Bull. — Clover farming. 323. 

64. U. S. Dept. Agr. Farmers' Btill.- — Soy beans. 372. 

65. U. S. Dept. Agr. Farmers' Bull. — The peanut. 431. 

66. U. S. Dept. Agr. Farmers' Bull. — Red clover. 455. 

67. U. S. Dept. Agr. Farmers' Bull. — Sweet clover. 485 

68. U. S. Dept. Agr. Farmers' Bull. — Forage crops for cotton. 509. 

69. U. S. Dept. Agr. Farmers' Bull.— Vetches. 515. 

70. U. S. Dept. Agr. Farmers' Bull. — Vetch growing. 529. 

71. LT. S. Dept. Agr. Farmers' Bull. — Crimson clover. 550. 

72. U. S. Dept. Agr. Farmers' Bull. — Cowpeas. 559. 

73. v. S. Dept. Agr. Farmers' Bull. — Crimson clover. 579. 

74. Univ. S. Calif. — Use of explosives in agriculture. Bull. 7. 1913. 

75. LTtah Agr. Coll. — Nitrogen fixation. Bull. 114. 




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Photographed Feb. 24th, 1915 Courtesy Armour Fertilizer Works 

Corn Stimulated with Inoculated Beans Corn not Stimulated 

Common Vetch 16 days old 



LIBRARY OF CONGRESS 



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